In addition, the 10-mile extension of the I-85 express lanes in Gwinnett County is set to open this fall.
The network of toll lanes is GDOT's solution to metro Atlanta's traffic congestion – which has been called some of the worst in the world.
For motorists willing to pay a toll of up to 90 cents a mile, the lanes should keep traffic flowing at least at 45 mph, even if traffic in the regular lanes is stopped. The worse the traffic, the higher the toll. The idea is to raise the fee high enough to discourage some people from using the toll lanes, meaning traffic should keep moving.
GDOT Commissioner Russell McMurry has said toll lanes are more effective at managing traffic than the addition of "free" lanes, which fill up as soon as they open. Some motorists love the lanes, while others dismiss them as "Lexus lanes" for those who can afford them.
The first 15 miles of toll lanes opened on I-85 in Gwinnett and DeKalb counties in 2011. Another 12 miles opened on I-75 in Clayton and Henry counties in January 2017.
Carpenter said the $834 million Northwest Corridor lanes on I-75 and I-575 in Cobb and Cherokee counties should open by the end of August. The lanes will stretch from I-285 to Hickory Grove Road on I-75 and to Sixes Road on I-575.
Like the other I-75 lanes, the Northwest Corridor will be reversible, carrying traffic into the city in the morning and out of town in the afternoon. The other planned express lanes are not reversible.
GDOT also is extending the I-85 lanes about 10 miles from Old Peachtree Road to Hamilton Mill Road. The $178 million project should be finished before Thanksgiving.
Over the next decade, the state plans to build toll lanes along the top half of the Perimeter and up Ga. 400. In the long term, it may also add them on I-20 east and west of the Perimeter and on I-75 south of the Perimeter (extending the existing lanes).
The Ga. 400 lanes got a recent boost from a $184 million federal grant. Gov. Nathan Deal also announced plans to spend $100 million on bus rapid transit infrastructure along Ga. 400 – a sign that state transportation officials see the toll lanes as transit corridors as well as highways.